Substrate material for mounting a semiconductor device, substrate for mounting a semiconductor device, semiconductor device, and method of producing the same

1. A substrate material for mounting a semiconductor device, comprising: an aluminum/silicon carbide (Al--SiC) composite alloy comprising an Al--SiC alloy composition having an aluminum or aluminum alloy matrix and granular silicon carbide particles dispersed therein and silicon as a component of a solid solution or as a precipitate in an amount no larger than 3% by weight, wherein said granular silicon carbide particles are dispersed in a concentration of from 10 to 70% by weight and are distributed substantially homogeneously such that fluctuations of the silicon carbide concentration within the Al--SiC composite alloy are less than 1%.

2. The substrate material for mounting a semiconductor device, as set forth in claim 1, wherein the substrate material has a thermal conductivity of 100 W/m.times.K or higher and a thermal expansion coefficient of 20.times.10.sup.-6 /.degree. C. or lower.

3. The substrate material for mounting a semiconductor device as claimed in claim 1, wherein the silicon carbide granular particles are dispersed from 35 to 70% by weight.

4. The substrate material for mounting a semiconductor device, as set forth in claim 3, wherein the substrate material has a thermal conductivity of 180 W/m.times.K or higher.

5. The substrate material for mounting a semiconductor device as set forth in claim 1, wherein said aluminum/silicon carbide composite alloy comprises: aluminum or aluminum alloy; silicon carbide; and aluminum carbide formed at an interface between said aluminum or aluminum alloy and said silicon carbide.

6. The substrate material for mounting a semiconductor device as claimed in claim 5, wherein the amount of the aluminum carbide is lower than 5% by weight.

7. The substrate material for mounting a semiconductor device as claimed in claim 6, wherein the aluminum/silicon carbide composite alloy has a thermal conductivity of 180 W/m.times.K or higher.

8. The substrate material for mounting a semiconductor device as claimed in claim 5, wherein aluminum carbide is distributed at the interface between the silicon carbide and the aluminum or aluminum alloy in such an amount that the ratio of the peak intensity for aluminum carbide (012) to that for aluminum (200) both determined by X-ray analysis with CuK.sub.a line is not more than 0.025.

9. The substrate material for mounting a semiconductor device as claimed in claim 8, wherein the aluminum/silicon carbide composite alloy has a thermal conductivity of 180 W/m.times.K or higher.

10. The substrate material for mounting a semiconductor device as claimed in claim 1, wherein the aluminum/silicon carbide composite alloy contains nitrogen in an amount of from 0.01 to 1% by weight.

11. The substrate material for mounting a semiconductor device as claimed in claim 1, wherein the aluminum/silicon carbide composite alloy contains oxygen in an amount of from 0.05 to 0.5% by weight.

12. The substrate material for mounting a semiconductor device as claimed in claim 1, wherein the aluminum/silicon carbide composite alloy contains .beta.-SiC as the silicon carbide granular particles.

13. The substrate material for mounting a semiconductor device as claimed in claim 1, wherein the silicon carbide granular particles have an average particle diameter of from 1 to 100 .mu.m.

14. The substrate material for mounting a semiconductor device as claimed in claim 12, wherein the silicon carbide granular particles have an average particle diameter of from 10 to 80 .mu.m.